Hearing loss is a common side effect of cisplatin, a drug commonly use for cancer treatment. Limited number of genome-wide association studies (GWAS) have been performed on a few hundred patients and only a handful of variants have been identified. Only 1 variant (rs1872328), in ACYP2 have been shown to be robustly associated with cisplatin associated hearing loss (CAHL). While this variant has such a large effect, it remains unclear what is the underlying biological mechanisms are and how they can be exploited as a treatment option. One reason why such findings are rare to begin with is that the sample size used for GWAS is small, as it is difficult to recruit patients for research if they are not already undergoing cisplatin treatment. Here, we plan to further test and identify genetic contributions to CAHL but with a different approach. Instead of CAHL, we propose to test otic progenitor cells derived from human individuals for cisplatin induced cytotoxity and use that as our phenotype instead. We propose to test these cells for their susceptibility to cisplatin induced toxicity. While extracting biological samples (PBMCs, Fibroblasts, etc) from a given individual, reprogramming them into pluripotent stem cells (iPSCs), differentiating the iPSCs into otic progenitors and testing them for cisplatin induced toxicity might be realistically attainable for 1 individual, doing so on cells from hundreds of different donors would be tedious. As such, we propose to employ our newly published method (Chan et. al., Genome Medicine, 2018) that would be able to multiplex test cellular phenotypes from many different donors by pooling the cells together, yet be able to extract individual level phenotypes from each donor. Having this method would tremendously reduce the cost and time needed to perform the experiment as instead of doing the experiments separately on thousands of different donor cells, we just have to do them once on a pool of cells from many different donors. Also, instead of obtaining cells directly from individuals, we propose to purchase lymphoblastoid cells from the Coriell Institute for Medical Research (CIMR), where they have biobanked cells obtained from many different donors, e.g. 1000 Genomes Project and Personal Genome Project and whole- genome genotype data are available for every donor. We aim to determine if otic progenitor cells from donors carrying the rs1872328 risk allele are more susceptible to cisplatin than non-carriers. Doing so will prove that this in-vitro phenotype can be effecitively used as a proxy for CAHL. Next, we aim to determine to what extent is cisplatin-induced ototoxicity is genetically determined by measuring the heritability using donor cells from related individuals. Finally, we aim to discover additional variants associated with CAHL by effectively performing a GWAS with cisplatin-induced ototoxcitiy as the phenotype. This will allow for the discovery of new pathways and potentially better target for treatment of CAHL. Our proposal offers a different approach to CAHL research where the phenotype is determined from experiments performed on cells obtained from donors rather than a clinical outcome of hearing loss as measured in human patients.